I'm 31 and I've been on the pill since I was 17. When I first started I put on weight - but my diet was terrible too so I can't really blame the pill!
I think it depends on what type of pill you're on. If it's just a normal run-of-the-mill kind, I don't think it really makes much diffence. If it's an especially strong pill it might...?
I've probably not really been much help have I?!
In my opinion though, as long as you're exercising and eating well, you'll lose weight...the pill won't make that much difference!